Chronic spontaneous urticaria (CSU) is a heterogeneous condition that can coexist with inducible urticaria subtypes and systemic abnormalities, complicating diagnosis and management. The incidental finding of monoclonal gammopathy in such patients may raise suspicion for rare autoinflammatory disorders, particularly Schnitzler syndrome (SchS), making careful differential diagnosis essential. We report a 58-year-old male with a 4-year history of recurrent urticaria triggered by exertion, heat, and emotional stress. Laboratory evaluation revealed elevated immunoglobulin M (IgM) level with monoclonal gammopathy, positive autologous serum skin test (ASST), and a positive exercise challenge test. Although both major Strasbourg criteria for SchS were present, no minor criteria were fulfilled. A diagnosis of CSU with coexisting cholinergic urticaria was established, and continuous treatment with second-generation antihistamines resulted in clinical improvement. This case highlights the importance of careful differential diagnosis in patients with CSU and monoclonal gammopathy. The presence of MGUS requires multidisciplinary evaluation and long-term hematologic follow-up.